The conservative Bradley Foundation has spent millions over three decades to smash labor unions. Now an investment that could barely buy a house in Washington may bring it closer to that goal than ever before.

The vehicle is a Supreme Court case, Friedrichs v. California Teachers Association, to bar public employee unions from compelling payments from nonmembers. The lawsuit, about which the high court will hear arguments Monday, was brought by Rebecca Friedrichs and eight other California public school teachers who declined to join the union that represents them in collective bargaining. But the lawsuit's true author looks to be the Milwaukee-based Lynde and Harry Bradley Foundation.

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The Bradley Foundation funds the Center for Individual Rights, the conservative D.C. nonprofit law firm that brought the case; it funds (or has funded) at least 11 organizations that submitted amicus briefs for the plaintiffs; and it's funded a score of conservative organizations that support the lawsuit's claim that the "fair-share fees" nonmembers must pay are unconstitutional. When CIR first filed the case in a California federal court in 2013, the Bradley Foundation posted the news on its website under the tab, "What We Do."

Bradley isn't the sole conservative philanthropy to bankroll CIR. Others have included Donors Capital Fund and Donor's Trust, two vehicles frequently used by the Koch brothers; the Dunn's Foundation for the Advancement of Right Thinking; the F.M. Kirby Foundation; the Lillian Wells Foundation; and the Carthage Foundation, according to Conservative Transparency, a project of the liberal opposition research nonprofit American Bridge.

But it's Bradley - with an endowment estimated at $800 million - that's provided the most conspicuously extensive support to Friedrichs. Since 1989, CIR (which bills itself as the conservative alternative to the American Civil Liberties Union) has received more than $2 million from the Bradley Foundation, according to data compiled by Conservative Transparency. Bradley continues to fund CIR through a general operating grant, CIR President Terry Pell told POLITICO.

The millions that Bradley has given the CIR are more than enough to finance the Friedrichs lawsuit. Indeed, tax filings indicate that CIR spent only $188,000 on Jones Day and its all-star litigator Michael Carvin - one of the Obama administration's biggest high court foes - between April 2014 and April 2015.

The litigation came cheap because Associate Justice Samuel Alito practically invited the case to be brought in two prior decisions, 2011's Knox v. SEIU and 2014's Harris v. Quinn. After the Knox decision, CIR filed its case in California, almost immediately asking the court to dismiss it. The only way it could win was at the Supreme Court, it said. That made one of the most consequential cases against U.S. labor unionism a bargain. "It is expensive enough," Pell told POLITICO. "But it is not overwhelmingly expensive."

Other conservative groups backing the Friedrichs case have also gained Bradley support, including the National Right to Work Legal Defense Foundation; the Goldwater Institute; the National Federation of Independent Businesses; the Freedom Foundation; the Atlantic Legal Foundation; and the Friedman Foundation for Educational Choice, according to Conservative Transparency data.

Founded in 1942 after the death of Lynne Bradley, co-founder of the Allen-Bradley Company, a successful Milwaukee manufacturer of electrical factory instruments, the Bradley Foundation was a modest enterprise focused on uncontroversial local philanthropy until 1985, when the company's purchase by Rockwell International vastly expanded its endowment.

Bradley hired Michael Joyce, a top officer of the conservative John Olin Foundation, to be its chairman, and the foundation shifted its focus to bankrolling conservative causes like school choice. The prominent neoconservative writer-editor Irving Kristol dubbed Joyce "the godfather of modern philanthropy." According to the Milwaukee Journal Sentinel, Bradley spent, between 2001 and 2009, nearly as much as the foundations associated with the Koch brothers and conservative philanthropist Richard Mellon Scaife, combined. The Bradley Foundation's endowment is today estimated at $800 million.

Joyce's successor was Michael Grebe, who had chaired Ronald Reagan's Wisconsin reelection campaign for president and become a mentor to a Marquette undergraduate named Scott Walker. Joyce served on Walker's transition after he was elected governor of Wisconsin and directed $1 million of Bradley's money to a local think tank that fed Walker policy proposals, many of them directed at curbing Wisconsin's public employee unions. After Walker eviscerated the unions' collective bargaining rights in the state, he hired Grebe to be chairman of his presidential campaign.

Bradley had already supported efforts to make Michigan and then Wisconsin - bastions of U.S. industrial union power - right-to-work states, meaning no unions, public or private, could charge fees to nonmembers. When Walker last year signed right-to-work into law he brought the number of right-to-work states to 25 — California, where the Friedrichs plaintiffs reside, not among them.

POLITICO requested comment from Grebe and the Bradley Foundation four times by phone and email but did not receive a response.

Even in California, the Friedrichs plaintiffs are already free from any obligation to provide financial support to any political activity that the teacher's union engages in. But they maintain that even their obligation to cover collective bargaining costs constitutes compelled speech that violates their First Amendment rights.

"Increasingly I saw that many of the things the union bargained for actually made my job as a teacher harder," Friedrichs told reporters Thursday. "Because of tenure laws, it is almost impossible to fire incompetent, and sometimes even abusive, teachers. And because of seniority-based layoff policies - last-in, first-out - which the union has negotiated, newer teachers are the first to go regardless of how good they are."

Should the Supreme Court rule for Friedrichs, as the conservative majority, prodded by Alito, will be sorely tempted to, the result will likely be a substantial loss of membership and revenue for public sector unions. That's because members in non-right-to-work states will find themselves newly able to receive the benefits of a union contract without having to pay for them. Public-sector unions make an especially inviting conservative target because they're the only pillar left in the U.S. labor movement: Nearly 36 percent of public-sector workers are unionized, even as membership among private-sector workers has dwindled from a comparable proportion in the 1950s to less than 7 percent today.

A decision for the Friedrichs plaintiffs would not affect private-sector unions because most of these are governed separately under the National Labor Relations Act, from which public-sector workers are excluded. Nor would it necessarily lead to a later decision applying the same reasoning to private unions, since the high court gives broader deference to First Amendment considerations in cases that involve the government.

It would nonetheless be a powerful blow against the Democratic Party, which has long relied on union funding from public-sector unions like the the 3 million-member National Education Association, the 1.4 million-member American Federation of Teachers and the 1.6 million members ofAmerican Federation of State, County, and Muncipal Employees. These are all pre-primary endorsers of Democratic presidential candidate Hillary Clinton. AFT President Randi Weingarten is also a close friend of Clinton and sits on the board of pro-Clinton Super PAC Priorities Action U.S.A.

Another major union threatened by the case is the 2 million-member Service Employees International Union, a Democratic stalwart that's also endorsed Clinton (even though its President Mary Kay Henry says 36 percent of its public members identify as conservative).

CIR's Pell told reporters Thursday that no outside group directed the case. "Donors expect us to tell them which cases we ought to be litigating," Pell said. "And certainly in this case we were not contacted by any donors about this. This was a case we put together with Jones Day and told our donors about it. The first they heard about it was after we filed the case."

But it was Pell who contacted Friedrich, additional teacher plaintiffs and others to bring the test case, not the other way around. "We looked for ways to find agency-fee payers," Pell told reporters. "We frankly thought it was going to take some number of months, maybe even a year to find clients for this case ... we were pleasantly surprised when we learned that there are a lot of teachers in California who ... were already focused on this issue."